You collect a random sample of 28 adult golfers and record two scores for each: one taken before the subject receives professional coaching and one taken after. What test statistic should you use in a significance test for the difference between the before-coaching scores and the after-coaching scores?

Paired t test

Step-by-step explanation:

Given that you collect a random sample of 28 adult golfers and record two scores for each: one taken before the subject receives professional coaching and one taken after.

Here subject of interest is to study whether the professional coaching really improves the scores.

For this two groups are taken from golfers and they were given chances to play and scores were recorded before and after coaching. The same subject with two different scores recorded and the difference calculated. Hence here the appropriate test is paired t test

Statistic should be t because population std devition is not known.

Hence paired t test for comparison of mean differences before and after should be done.